Rotor assembly, motor including rotor assembly, and method for manufacturing rotor assembly

ABSTRACT

A rotor assembly includes a shaft including a non-magnetic material and a central axis extending along an up and down direction as a center, and a cylindrical rotor main body fixed to an outer surface of the shaft. The rotor main body includes core pieces arranged around the shaft in a circumferential direction, rotor magnets alternately arranged with the core pieces around the shaft in the circumferential direction, and a connection portion made of resin and connecting the shaft to the core pieces and the rotor magnets. Inner ends of the rotor magnets in a radial direction are closer to the shaft than inner ends of the core pieces in the radial direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application No. 2017-155394 filed on Aug. 10, 2017. The entire contents of this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a rotor assembly and a method for manufacturing a rotor assembly.

2. Description of the Related Art

In the related art, an inner rotor type motor in which a rotor is disposed inward a stator in a radial direction is known. In the motor, in the rotor, a plurality of magnets and a plurality of yokes are disposed alternately in a circumferential direction around a rotation shaft made of iron. A cylindrical gap portion for preventing the formation of a magnetic path is formed between an outer circumferential surface of the rotation shaft and inner circumferential surfaces of the magnet and the yoke. A cylindrical member made of a non-magnetic material is inserted into the gap portion. Between the cylindrical member, the magnet, and the yoke, a resin material is impregnated and cured.

Incidentally, in the motor, upon assembly of the rotor, when the rotation shaft, the magnet, and the like are disposed in a metal mold or the like, there is a possibility that the rotation shaft shakes or the magnet is attracted to the rotation shaft, by the magnetic force acting between the rotation shaft and the magnet. Therefore, it is necessary to maintain the relative position between the rotation shaft and the magnet by using a positioning jig or the like, and there is a possibility that manufacturing of the rotor becomes complicated.

SUMMARY OF THE INVENTION

According to an exemplary embodiment of the present disclosure, a rotor assembly includes a shaft including a non-magnetic material and a central axis extending along an up and down direction as a center; and a cylindrical rotor main body fixed to an outer surface of the shaft. The rotor main body includes a plurality of core pieces arranged around the shaft in a circumferential direction, a plurality of rotor magnets alternately arranged with the plurality of core pieces around the shaft in the circumferential direction, and a connection portion that is made of resin and connects the shaft to the plurality of core pieces and the plurality of rotor magnets. Inner ends of the plurality of rotor magnets in a radial direction are closer to the shaft than inner ends of the plurality of core pieces in the radial direction.

In addition, according to an exemplary embodiment of the present disclosure, a method for manufacturing an exemplary rotor assembly includes a) a step of disposing a shaft, which is made of a non-magnetic material and has a central axis extending along an up and down direction as a center, in a center of a cylindrical metal mold; b) a step of arranging a plurality of core pieces around the shaft in a circumferential direction, c) a step of arranging a plurality of rotor magnets alternately with the plurality of core pieces around the shaft in the circumferential direction, and d) a step of connecting the shaft to the plurality of core pieces and the plurality of rotor magnets by filling with resin a space between the shaft, the plurality of core pieces, and the plurality of rotor magnets. In step b), outer surfaces of the plurality of core pieces abut against an inner surface of the metal mold.

In step c), outer surfaces of the plurality of rotor magnets abut against the inner surface of the metal mold. Inner ends of the plurality of rotor magnets in a radial direction are closer to the shaft than inner ends of the plurality of core pieces in the radial direction.

The above and other elements, features, steps, characteristics, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating a motor according to an exemplary embodiment of the present disclosure.

FIG. 2 is a perspective view illustrating an internal structure of the motor of FIG. 1.

FIG. 3 is a transverse sectional view illustrating the motor of FIG. 1.

FIG. 4 is a longitudinal sectional view illustrating the motor of FIG. 1.

FIG. 5 is a perspective view illustrating the internal structure of the motor of FIG. 1 by omitting a connection portion.

FIG. 6 is a longitudinal sectional view illustrating a rotor magnet according to an exemplary embodiment of the present disclosure.

FIG. 7 is a transverse sectional view illustrating of the rotor magnet of FIG. 6.

FIG. 8 is a view illustrating a flow of manufacturing a rotor assembly according to an exemplary embodiment of the present disclosure.

FIG. 9 is a transverse sectional view illustrating a rotor assembly according to an exemplary embodiment of the present disclosure in the course of manufacture.

FIG. 10 is a longitudinal sectional view illustrating a rotor assembly according to an exemplary embodiment of the present disclosure in the course of manufacture.

FIG. 11 is a longitudinal sectional view of another motor according to an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a side view illustrating an outer appearance of a motor 1 according to an exemplary embodiment of the present disclosure. The motor 1 is an inner rotor type brushless motor. The motor 1 is used, for example, to rotate an impeller in an axial flow fan. FIG. 2 is a perspective view illustrating an internal structure of the motor 1. In FIG. 2, a portion of the housing 21 or the like of the motor 1 is omitted for illustration. FIG. 3 is a transverse sectional view of the motor 1. FIG. 4 is a longitudinal sectional view of the motor 1 cut at position IV-IV in FIG. 3. In FIG. 3 and FIG. 4, parallel slanted lines in the detailed cross section are omitted.

In this specification, an upper side in a direction of a central axis J1 of the motor 1 in FIG. 4 is simply referred to as “upper side”, and a lower side is simply referred to as “lower side”. The upper side and the lower side in this specification do not indicate the upper side and the lower side in the direction of gravity when incorporated in actual equipment.

In the following description, a circumferential direction which has the central axis J1 as a center is simply referred to as “circumferential direction”, and the radial direction which has the central axis J1 as a center is simply referred to as “radial direction”. In addition, the direction parallel to the central axis J1 is referred to as “up and down direction”. The up and down direction is also an axial direction.

The motor 1 includes a stationary portion 2, a rotation portion 3, and a bearing mechanism 4. The bearing mechanism 4 rotatably supports the rotation portion 3 with respect to the stationary portion 2. The stationary portion 2 includes a housing 21, an armature 22, a bus bar 23, and a bus bar holding portion 24. The rotation portion 3 includes a rotor assembly 30 and a rotor fan 34. The rotor assembly 30 includes a shaft 31, a rotor main body 32, and a connection plate portion 33. The bearing mechanism 4 includes a first bearing 41 and a second bearing 42. The first bearing 41 and the second bearing 42 are, for example, ball bearings. The housing 21 is a substantially cylindrical member having a bottom and a lid, which has the central axis J1 along the up and down direction as a center. The housing 21 includes a side wall portion 211, a bottom portion 212, and a canopy portion 213. The side wall portion 211 is a substantially cylindrical portion which has the central axis J1 as a center. The bottom portion 212 is a substantially annular plate-shaped portion which has the central axis J1 as a center. The bottom portion 212 is connected to the lower end portion of the side wall portion 211 and covers a lower opening of the side wall portion 211. The canopy portion 213 is a substantially disk-like portion which has the central axis J1 as a center. The canopy portion 213 is connected to an upper end portion of the side wall portion 211 and covers the upper opening of the side wall portion 211.

In the housing 21, a plurality of first openings 215 are provided in an upper portion of the side wall portion 211. In an example illustrated in FIG. 1, four first openings 215 are positioned on the outer surface of the housing 21. The plurality of first openings 215 are arranged at substantially equal angular intervals in the circumferential direction at substantially the same position in the up and down direction. The plurality of first openings 215 are positioned above the armature 22. Each first opening 215 is a through hole penetrating the side wall portion 211 in the radial direction. Each of the first openings 215 is a substantially rectangular shape extending in the circumferential direction in a side view. The shape of the first opening 215 may be appropriately changed. The number of the first openings 215 may be 1, or 2 or more.

In addition, in the housing 21, a plurality of second openings 216 are provided in the outer peripheral portion of the bottom portion 212. The plurality of second openings 216 are positioned below the armature 22. The plurality of second openings 216 are arranged at substantially equal angular intervals in the circumferential direction at substantially the same position in the radial direction. Each second opening 216 is a through hole penetrating the bottom portion 212 in the up and down direction. Each of the second openings 216 is a substantially rectangular shape in a plan view. The shape of the second opening 216 may be appropriately changed. The number of the second openings 216 may be 1, or 2 or more. In an example illustrated in FIG. 2, twelve second openings 216 which are equal in number to the teeth 222 (described below) of the armature 22 are positioned between the plurality of teeth 222 in the circumferential direction in the bottom surface of the housing 21.

The upper portion of the shaft 31, the rotor main body 32, the rotor fan 34, the armature 22, the bus bar 23, and the bus bar holding portion 24 are accommodated in the housing 21. The lower end portion of the shaft 31 protrudes downward from the bottom portion 212 of the housing 21. At the lower end portion of the shaft 31, for example, the impeller of an axial flow fan is attached.

The shaft 31 is a substantially columnar or substantially cylindrical member which has the central axis J1 as a center. In an example illustrated in FIG. 4, the shaft 31 is a substantially cylindrical member. Accordingly, it is possible to reduce the weight of the shaft 31 and the motor 1. The shaft 31 is, for example, a member made of a non-magnetic material. The shaft 31 is formed of, for example, stainless steel. The shaft 31 is rotatably supported by the bearing mechanism 4.

The first bearing 41 of the bearing mechanism 4 rotatably supports the upper end portion of the shaft 31 at the upper end portion in the housing 21. The first bearing 41 is a substantially cylindrical member which has the central axis J1 as a center. In the example illustrated in FIG. 4, the first bearing 41 is held by a bearing holding portion 214 of the housing 21. The bearing holding portion 214 is a substantially cylindrical portion protruding downward from the canopy portion 213 of the housing 21 toward the inside of the housing 21. The bearing holding portion 214 is in contact with the outer surface of the first bearing 41 and holds the first bearing 41.

The second bearing 42 of the bearing mechanism 4 is positioned below the first bearing 41 and rotatably supports the lower portion of the shaft 31. The second bearing 42 is positioned, for example, below the rotor main body 32. The second bearing 42 is a substantially cylindrical member which has the central axis J1 as a center. The outer diameter of the second bearing 42 is, for example, smaller than the outer diameter of the first bearing 41. In the example illustrated in FIG. 4, the second bearing 42 is positioned substantially at the same position as the bottom portion 212 of the housing 21 in the up and down direction. The second bearing 42 is held by the bottom portion 212 of the housing 21.

The rotor main body 32 is a substantially cylindrical member which has the central axis J1 as a center. The rotor main body 32 is fixed to the outer surface of the shaft 31. The rotor main body 32 is fixed to the shaft 31 by insert molding, for example. At both ends of the rotor main body 32 in the up and down direction, a substantially annular plate-like connection plate portion 33 is disposed. The rotor main body 32 is also connected to the shaft 31 by the connection plate portion 33. The connection plate portion 33 may be provided only at one of the upper end portion and the lower end portion of the rotor main body 32.

The rotor main body 32 includes a plurality of core pieces 321, a plurality of rotor magnets 322, and a connection portion 323. The plurality of core pieces 321 are made of magnetic metal. Each core piece 321 is formed by stacking in the up and down direction and caulking a plate member made of a magnetic metal such as a steel plate. The connection portion 323 is made of resin.

The plurality of core pieces 321 are arranged around the shaft 31 in the circumferential direction. The plurality of rotor magnets 322 are arranged alternately with the plurality of core pieces 321 around the shaft 31 in the circumferential direction. The plurality of core pieces 321 are disposed at substantially equal angular intervals. The plurality of rotor magnets 322 are also arranged at substantially equal angular intervals. In an example illustrated in FIG. 3, fourteen core pieces 321 and fourteen rotor magnets 322 are alternately arranged in the circumferential direction.

In the plan view, each core piece 321 is a portion of the substantially annular shape in the circumferential direction which has the central axis J1 as a center. Each rotor magnet 322 has a substantially rectangular shape extending along the radial direction in the plan view. The plan view is a shape of the object viewed from the upper side with a view line parallel to the central axis J1. The width of the outer surface of each core piece 321 in the circumferential direction is, for example, larger than the width of the outer surface of each rotor magnet 322 in the circumferential direction. The shapes of the core piece 321 and the rotor magnet 322 may be variously changed. The number of the core piece 321 and the rotor magnet 322 may be appropriately changed within a range of 2 or more, respectively.

In the rotor main body 32, a substantially cylindrical assembly is formed by the plurality of core pieces 321 and the plurality of rotor magnets 322. The outer surfaces of the plurality of core pieces 321 and the outer surfaces of the plurality of rotor magnets 322 are positioned at substantially the same position in the radial direction. In other words, the distance between the central axis J1 and the outer surface of each core piece 321 in the radial direction and the distance between the central axis J1 and the outer surface of each rotor magnet 322 in the radial direction are substantially the same. Accordingly, the leakage magnetic flux from the rotor magnet 322 can be reduced and the output of the motor 1 can increase. In addition, the inner ends of the plurality of rotor magnets 322 in the radial direction are closer to the shaft 31 than the inner ends of the plurality of core pieces 321 in the radial direction. In other words, the distance between the inner end in the radial direction of each rotor magnet 322 and the shaft 31 in the radial direction is smaller than the distance between the inner end in the radial direction of each core piece 321 and the shaft 31 in the radial direction. In other words, the inner ends of the plurality of rotor magnets 322 in the radial direction protrude inward from the inner surfaces of the plurality of core pieces 321 in the radial direction.

The upper end of each core piece 321 is positioned below the upper end of each rotor magnet 322. The lower end of each core piece 321 is positioned above the lower end of each rotor magnet 322. In other words, the upper end portion and the lower end portion of the plurality of rotor magnets 322 protrude from the upper end and the lower end of the plurality of core pieces 321 in the up and down direction.

The connection portion 323 is a substantially cylindrical portion which has the central axis J1 as a center. The connection portion 323 connects the shaft 31 to the plurality of core pieces 321 and the plurality of rotor magnets 322. The connection portion 323 is formed by filling a space between the shaft 31 and the plurality of core pieces 321 and the plurality of rotor magnets 322 with resin. In other words, the connection portion 323 fills the space between the shaft 31 and the plurality of core pieces 321 and the plurality of rotor magnets 322.

At the central portion of the upper end surface of the connection portion 323, a central protrusion portion 326 protruding upward from a region around the upper end surface is provided. The central protrusion portion 326 is a substantially cylindrical portion in contact with the outer surface of the shaft 31. The outer surface of the central protrusion portion 326 is an inclined surface facing inward in the radial direction as the outer surface thereof goes upward.

The connection portion 323 covers an outer surface of the shaft 31, an inner surface positioned inward of the surface of each of the respective core pieces 321 in the radial direction, an inner surface positioned inward of the surface of the rotor magnet 322 in the radial direction, and the inner end portions in the radial direction of both side surfaces of each of the rotor magnet 322 in the circumferential direction. A core recessed portion 324 recessed outward in the radial direction is provided on the inner surface of each core piece 321. In the vicinity of the inner surface of the core piece 321, the width of the core recessed portion 324 in the circumferential direction gradually increases as the core recessed portion goes farther outward from the inner surface of the core piece 321 in the radial direction. The maximum width of the core recessed portion 324 in the circumferential direction is larger than the width of the core recessed portion 324 in the circumferential direction on the inner surface of the core piece 321.

In the core recessed portion 324, the resin of the connection portion 323 is present. A portion of the connection portion 323 positioned in the core recessed portion 324 and a portion of the connection portion 323 positioned inward of the inner surface of the core piece 321 in the radial direction are continuous resin members which are connected to each other via the opening at the inner end of the core recessed portion 324 in the radial direction. The connection portion 323 also covers both end surfaces of the plurality of core pieces 321 and the plurality of rotor magnets 322 in the up and down direction.

FIG. 5 is a perspective view of the motor 1 in which the connection portion 323 of FIG. 2 is not illustrated. Each connection plate portion 33 includes a first portion 331 and a plurality of second portions 332. The first portion 331 has a substantially annular shape which has the central axis J1 as a center. The plurality of second portions 332 extend radially outward from the outer peripheral edge of the first portion 331 in the radial direction. The plurality of second portions 332 are arranged at substantially equal angular intervals in the circumferential direction. The number of the plurality of second portions 332 is the same as the number of the plurality of core pieces 321. The shape of each second portion 332 in the plan view is substantially the same as the shape of the core piece 321 in the plan view.

The first portion 331 of the connection plate portion 33 is connected to the outer surface of the shaft 31 by press fitting or the like. The plurality of second portions 332 overlap the plurality of core pieces 321 in the up and down direction. Both end surfaces of each core piece 321 in the up and down direction are covered by the second portion 332 of the connection plate portion 33. The plurality of second portions 332 come in contact with the end surfaces of the plurality of core pieces 321 in the up and down direction and are connected to the plurality of core pieces 321. Accordingly, the plurality of core pieces 321 of the rotor main body 32 and the shaft 31 are connected, and the plurality of core pieces 321 are prevented from shifting with respect to the shaft 31 in the circumferential direction. The connection plate portion 33 and the plurality of core pieces 321 are connected to each other by inserting pins protruding from the end surfaces of the respective core pieces 321 in the up and down direction into the holes provided in the respective second portions 332 of the connection plate portion 33. In the example illustrated in FIG. 4, among the two connection plate portions 33, only the lower connection plate portion 33 is directly connected to the outer surface of the shaft 31, and the upper connection plate portion 33 is slightly spaced from the outer surface of the shaft 31.

Both end surfaces of the plurality of rotor magnets 322 in the up and down direction are positioned between the plurality of second portions 332 in the circumferential direction. In other words, both end surfaces of each rotor magnet 322 in the up and down direction are not substantially covered by the connection plate portion 33, but are exposed from between the two second portions 332 adjacent in the circumferential direction. The upper end of each rotor magnet 322 is positioned at substantially the same position in the up and down direction as the upper end surface of each second portion 332 of the upper connection plate portion 33. The lower end of each rotor magnet 322 is positioned at substantially the same position in the up and down direction as the lower end surface of each second portion 332 of the lower connection plate portion 33.

As illustrated in FIGS. 2 and 4, the connection portion 323 of the rotor main body 32 covers the both end surfaces of a plurality of core pieces 321 and a plurality of rotor magnets 322 from above the connection plate portion 33 on both sides of the plurality of core pieces 321 and the plurality of rotor magnets 322 in the up and down direction. Since the end surface of each core piece 321 in the up and down direction is covered by the connection plate portion 33 as described above, the connection portion 323 indirectly come in contact with the end surface of each core piece 321 in the up and down direction via the connection plate portion 33. In addition, the connection portion 323 directly come in contact with the end surfaces of each of the rotor magnets 322 in the up and down direction without going via the connection plate portion 33.

FIG. 6 is an enlarged longitudinal transverse sectional view illustrating one rotor magnet 322 and vicinity thereof. In addition, in FIG. 6, a core piece 321 adjacent to the rotor magnet 322 is indicated by a two-dot chain line. FIG. 7 is an enlarged transverse sectional view illustrating the rotor magnet 322 and vicinity thereof. The shapes and structures of other rotor magnets 322 and vicinities thereof are substantially the same as those illustrated in FIGS. 6 and 7.

Among the surfaces of the rotor magnet 322, the upper end surface 351 and the lower end surface 352 are covered by the connection portion 323 over substantially the entire surface. In addition, among the surfaces of the rotor magnet 322, the inner surface 361 positioned inward in the radial direction is also covered by the connection portion 323 over substantially the entire surface. On the side surfaces 362 on both sides of the rotor magnet 322 in the circumferential direction, the region 365 of the inner end in the radial direction continuous from the inner surface 361 is covered by the connection portion 323, and the region other than the region 365 is covered by the adjacent core piece 321 in the circumferential direction. In the following description, the region 365 is referred to as “side surface inner end region 365”. The outer surface 363 of the surfaces of rotor magnet 322 positioned outward in the radial direction is not covered by the connection portion 323, the core piece 321 and the like over substantially the entire surface, but is exposed from the connection portion 323 and the core piece 321. In other words, the outer surface 363 of the rotor magnet 322 is a portion of the outer surface of the rotor main body 32.

In the following description, among the surface of the rotor magnet 322, a region covered by the connection portion 323 is referred to as an “engagement region 371”, and a region exposed from the connection portion 323 is referred to as an “exposed region 372”. The engagement region 371 includes a side surface inner end region 365 of an upper end surface 351, a lower end surface 352, an inner surface 361, and side surfaces 362 on both ends of the rotor magnet 322. The exposed region 372 includes the outer surface 363 of the rotor magnet 322.

The upper end surface 351 of the rotor magnet 322 includes a first region 353 and a second region 354. The first region 353 is positioned inward in the radial direction on the upper end surface 351. The inner end of the first region 353 in the radial direction is, for example, the inner end of the upper end surface 351 in the radial direction. The second region 354 is continuous with the outer end of the first region 353 in the radial direction. The second region 354 extends outward in the radial direction from the outer end of the first region 353 in the radial direction. The outer end of the second region 354 in the radial direction is, for example, the outer end of the upper end surface 351 in the radial direction. The outer end of the second region 354 in the radial direction is an end positioned on the side opposite to the first region 353 in the second region 354. The radial outer end of the second region 354 may be positioned inward in the radial direction of the outer end of the upper end surface 351 in the radial direction.

The outer end of the second region 354 in the radial direction is positioned below the first region 353. In other words, the outer end of the second region 354 in the radial direction is closer to the lower end surface 352 of the rotor magnet 322 than the first region 353. The second region 354 approaches the lower end surface 352 of the rotor magnet 322 as the second region moves away from the outer end of the first region 353 in the radial direction. In an example illustrated in FIG. 6, the second region 354 is an inclined surface which gradually approaches the lower end surface 352 in the up and down direction as the second region moves away from the first region 353 outward in the radial direction. The second region 354 is a flat surface in which the inclination angle with respect to the horizontal plane is substantially constant over substantially the entire length in the radial direction. In addition, the first region 353 is a plane substantially vertical to the up and down direction.

In FIG. 6, a normal vector 355 of the second region 354 is indicated by thick arrow. The normal vector 355 of the second region 354 has a component facing outward in the radial direction. In other words, the second region 354 is positioned at the same position in the up and down direction as a portion covering the second region 354 of the connection portion 323, and faces in the radial direction. In other words, the second region 354 of the upper end surface 351 is an engagement surface that engages in the radial direction with a portion of the connection portion 323 covering the second region 354.

Similarly to the upper end surface 351, the lower end surface 352 of the rotor magnet 322 includes a first region 356 and a second region 357. The first region 356 is positioned inward in the radial direction on the lower end surface 352. The inner end of the first region 356 in the radial direction is, for example, the inner end of the lower end surface 352 in the radial direction. The second region 357 is continuous with the outer end of the first region 356 in the radial direction. The second region 357 extends outward in the radial direction from the outer end of the first region 356 in the radial direction. The outer end of the second region 357 in the radial direction is, for example, an outer end of the lower end surface 352 in the radial direction. The outer end of the second region 357 in the radial direction is an end positioned on the side opposite to the first region 356 in the second region 357. The outer end of the second region 357 in the radial direction may be positioned inward in the radial direction of the outer end of the lower end surface 352 in the radial direction.

The outer end of the second region 357 in the radial direction is positioned above the first region 356. In other words, the outer end of the second region 357 in the radial direction is closer to the upper end surface 351 of the rotor magnet 322 than the first region 356. The second region 357 approaches the upper end surface 351 of the rotor magnet 322 as the second region moves away from the outer end of the first region 356 in the radial direction. In an example illustrated in FIG. 6, the second region 357 is an inclined surface which gradually approaches the upper end surface 351 in the up and down direction as the second region goes outward in the radial direction from the first region 356. The second region 357 is a flat surface in which the inclination angle with respect to the horizontal plane is substantially constant over almost the entire length in the radial direction. In addition, the first region 356 is a flat surface substantially perpendicular in the up and down direction.

In FIG. 6, a normal vector 358 of the second region 357 is indicated by thick arrow. The normal vector 358 of the second region 357 has a component facing outward in the radial direction. In other words, the second region 357 is positioned at the same position in the up and down direction as a portion covering the second region 357 of the connection portion 323, and faces the portion in the radial direction. In other words, the second region 357 of the lower end surface 352 is an engagement surface that engages in a radial direction with a portion of the connection portion 323 covering the second region 357.

FIG. 8 is a view illustrating a flow of manufacturing the rotor assembly 30. FIG. 9 is a transverse sectional view illustrating the rotor assembly 30 in the process of manufacture. FIG. 10 is a longitudinal sectional view illustrating a portion of the rotor assembly 30 in the process of manufacture. In FIGS. 9 and 10, the metal mold 91 used for manufacturing the rotor assembly 30 is also illustrated. FIG. 9 illustrates the state before Step S14 is completed after steps S11 to S13 to be described below are completed. FIG. 10 illustrates a state where step S14 is being performed.

When the rotor assembly 30 is manufactured, first, the shaft 31 made of a non-magnetic material is disposed at the center of a substantially cylindrical magnetic metal mold 91 (step S11). The inner surface 92 of the metal mold 91 is a substantially cylindrical surface which has the central axis as a center. The central axis of the inner surface 92 of the metal mold 91 coincides with the central axis J1 of the motor 1 described above.

Subsequently, the plurality of core pieces 321 are arranged in the circumferential direction around the shaft 31 in the metal mold 91 (step S12). For example, the plurality of core pieces 321 are handled in a state where the upper end surface and the lower end surface are connected by the connection plate portion (see FIG. 5). In step S12, the plurality of core pieces 321 are disposed away from the shaft 31 outward in the radial direction. In addition, the outer surface 325 of the plurality of core pieces 321 abuts against the inner surface 92 of the metal mold 91.

Next, the plurality of rotor magnets 322 are alternately arranged in the circumferential direction with the plurality of core pieces 321 around the shaft 31 in the metal mold 91 (step S13). In step S13, the plurality of rotor magnets 322 are disposed away from the shaft 31 outward in the radial direction. In addition, the outer surfaces 363 of the plurality of rotor magnets 322 abut against the inner surface 92 of the metal mold 91. As illustrated in FIG. 9, the inner ends of the plurality of rotor magnets 322 in the radial direction are closer to the shaft 31 than the inner ends of the plurality of core pieces 321 in the radial direction. In addition, the first regions 353 and 356 (see FIG. 6) of the upper end surface 351 and the lower end surface 352 of each rotor magnet 322 are positioned substantially at the same positions in the up and down direction with the end surfaces of the upper and lower connection plate portions 33.

In steps S12 and S13, a plurality of rotor magnets 322 and a plurality of core pieces 321 alternately arranged in the circumferential direction are coupled by the magnetic force of the rotor magnet 322. In addition, the outer surface 363 of the plurality of rotor magnets 322 and the outer surface 325 of the plurality of core pieces 321 are attracted to and abut against the inner surface 92 of the metal mold 91 by the magnetic force of the rotor magnet 322. Step S13 may be performed before step S12. Alternatively, step S12 and step S13 may be performed in parallel.

When steps S11 to S13 are completed, as illustrated in FIG. 10, the resin 95 is poured into the metal mold 91 from a plurality of gates 94 provided on the upper portion of the metal mold 91. The gate 94 faces the connection plate portion 33 and the core piece 321 illustrated on the left side in FIG. 10 and the rotor magnet 322 illustrated on the right side of FIG. 10 in the up and down direction via a gap. The resin 95 poured into the metal mold 91 from the gate 94 is filled in a space 93 between the shaft 31 and the plurality of core pieces 321 and the plurality of rotor magnets 322. The connection portion 323 is formed by hardening the resin 95, and the shaft 31, the plurality of core pieces 321, and the plurality of rotor magnets 322 are connected by the connection portion 323 (step S14). In addition, the connection portion 323 also covers both upper end surfaces of the plurality of core pieces 321 and the plurality of rotor magnets 322 in the up and down direction, and the connection plate portion 33. Then, when the metal mold 91 is removed, the manufacture of the rotor assembly 30 is completed. In step S14, in a case where there is a gap between the core piece 321 and the rotor magnet 322 that are adjacent in the circumferential direction, the gap may also be filled with resin.

In the example illustrated in FIG. 4, the rotor fan 34 is fixed to the shaft 31 on the upper side of the rotor main body 32. The first bearing 41 is positioned above the rotor fan 34. In other words, the rotor fan 34 is positioned between the first bearing 41 and the rotor main body 32 in the up and down direction. The rotor fan 34 faces the first bearing 41 and the rotor main body 32 in the up and down direction. The outer diameter of the rotor fan 34 is larger than the outer diameter of the first bearing 41 and larger than the outer diameter of the lower end portion of the bearing holding portion 214. In addition, the outer diameter of the rotor fan 34 is substantially equal to the outer diameter of the rotor main body 32. The outer diameter of the rotor fan 34 is twice the distance between an outermost edge of a blade 342 (described below) and the central axis J1 of the rotor fan 34 in the radial direction.

The rotor fan 34 is a substantially annular member surrounding the periphery of the shaft 31. The rotor fan 34 is, for example, a diagonal flow fan or a centrifugal fan. The rotor fan 34 includes a fan base portion 341 and a plurality of blades 342. The fan base portion 341 is a substantially annular portion which has the central axis J1 as a center. The fan base portion 341 is connected to the outer surface of the shaft 31 by press fitting or the like. The plurality of blades 342 are connected to the fan base portion 341. The plurality of blades 342 are arranged at substantially equal angular intervals in the circumferential direction.

The armature 22 faces the rotor main body 32 in the radial direction. The armature 22 includes a core back portion 221, a plurality of teeth 222, an insulator 223, and a plurality of coils 224. The core back portion 221 is a substantially cylindrical portion which has the central axis J1 as a center. The core back portion 221 is fixed to the inner surface of the side wall portion 211 of the housing 21. The plurality of teeth 222 extend radially inward from the core back portion 221 in the radial direction. The plurality of teeth 222 are arranged at substantially equal angular intervals in the circumferential direction. The core back portion 221 and the plurality of teeth 222 are, for example, members made of magnetic metal which are connected. The insulator 223 is an insulating body covering the surfaces of the plurality of teeth 222. The plurality of coils 224 are formed by winding a conductive wire from above the insulator 223 to the plurality of teeth 222. In the present embodiment, the plurality of coils 224 are three-phase coils.

The plurality of coils 224 are electrically connected to a plurality of bus bars 23 arranged above the armature 22. In the example illustrated in FIG. 4, the number of bus bars 23 is three. Each bus bar 23 is a conductive member. Each bus bar 23 is a substantially annular or substantially arcuate member which has the central axis J1 as a center. The plurality of bus bars 23 include a U-phase bus bar, a V-phase bus bar, and a W-phase bus bar. The U-phase bus bar connects the plurality of U-phase coils 224 among the plurality of coils 224 to each other. The V-phase bus bar connects the plurality of V-phase coils 224 among the plurality of coils 224 to each other. The W phase bus bar connects the plurality of W phase coils 224 among the plurality of coils 224 to each other. The plurality of bus bars 23 electrically connect the plurality of coils 224 of the armature 22 to an external power supply (not illustrated).

The plurality of bus bars 23 are held by the bus bar holding portion 24. The bus bar holding portion 24 is a substantially cylindrical member which has the central axis J1 as a center. The bus bar holding portion 24 is an insulating member. The bus bar holding portion 24 is arranged on the upper side of the armature 22 and faces the armature 22 in the up and down direction. In addition, the bus bar holding portion 24 is disposed outward of the rotor fan 34 in the radial direction and faces the rotor fan 34 in the radial direction. The bus bar holding portion 24 is fixed to the housing 21 or the armature 22, for example.

The bus bar holding portion 24 includes an inner cylindrical portion 241, a flange portion 242, and an outer cylindrical portion 243. The inner cylindrical portion 241 is a substantially cylindrical portion which has the central axis J1 as a center. The flange portion 242 is a substantially annular portion extending outward from the lower end portion of the inner cylindrical portion 241 in the radial direction. In the example illustrated in FIG. 4, the flange portion 242 faces downward as the flange portion goes outward in the radial direction. The outer cylindrical portion 243 faces downward from the outer end portion of the flange portion 242. The outer cylindrical portion 243 is a substantially cylindrical portion about the central axis J1. The inner cylindrical portion 241, the flange portion 242, and the outer cylindrical portion 243 are, for example, members made of resin which are connected.

In the bus bar holding portion 24, the outer surface of the outer cylindrical portion 243 comes in contact with the inner surface of the side wall portion 211 of the housing 21. The lower end portion of the outer cylindrical portion 243 comes in contact with the upper end portion of the core back portion 221 of the armature 22. The flange portion 242 is provided with a plurality of groove portions 244 opening upward. Each of the groove portions 244 is substantially annular or substantially arcuate which has the central axis J1 as a center. In each groove portion 244, the bus bar 23 is accommodated and fixed. In the example illustrated in FIG. 4, three bus bars 23 are fixed to the three groove portions 244 of the bus bar holding portion 24. The number of the bus bars 23 held by the bus bar holding portion 24 may be 1, or 2 or more. In addition, the bus bar 23 in the groove portion 244 may be molded with resin.

The bus bar holding portion 24 is a substantially cylindrical wind tunnel portion disposed outside the rotor fan 34 in the radial direction. The inner surface 245 of the inner cylindrical portion 241 of the bus bar holding portion 24 is substantially cylindrical which has the central axis J1 as a center. The inner surface 245 of the bus bar holding portion 24 faces the rotor fan 34 in the radial direction. The inner surface 245 of the bus bar holding portion 24 is positioned outward in the radial direction the outer edge of each blade 342 of the rotor fan 34 in the radial direction and is close to the outer edge of each blade 342 in the radial direction. The inner surface 245 of the bus bar holding portion 24 faces each blade 342 in the radial direction over substantially the entire length of each blade 342 in the up and down direction. The upper end of the inner surface 245 of the bus bar holding portion 24 is positioned above the upper ends of each blade 342 of the rotor fan 34.

The upper end portion of the inner surface 245 of the bus bar holding portion 24 faces the outer surface 217 of the bearing holding portion 214 in the radial direction. The outer surface 217 of the bearing holding portion 214 is an inclined surface that faces inward in the radial direction as outer surface goes downward. The outer surface 217 of the bearing holding portion 214 is, for example, a side surface of a substantially truncated cone. The outer surface 217 of the bearing holding portion 214 is positioned at substantially the same position in the up and down direction as each first opening 215 of the housing 21. In other words, each of the first openings 215 faces the outer surface 217 of the bearing holding portion 214 in the radial direction.

The lower surface 246 of the flange portion 242 of the bus bar holding portion 24 is a substantially annular surface which has the central axis J1 as a center. The lower surface 246 of the flange portion 242 extends outward from the lower end of the inner surface 245 of the inner cylindrical portion 241 in the radial direction. The lower surface 246 of the flange portion 242 is an inclined surface facing downward as the lower surface thereof faces outward from the lower end of the inner surface 245 in the radial direction. The lower surface 246 of the flange portion 242 is positioned between the armature 22 and the bus bar 23 which are arranged in the up and down direction. The lower surface 246 of the flange portion 242 faces the armature 22 in the up and down direction.

In the motor 1, a current is supplied to the coil 224 of the armature 22 via the bus bar 23, so that a torque is generated between the coil 224 and the rotor main body 32. Accordingly, the rotation portion 3, that is, the rotor assembly 30 and the rotor fan 34 rotate about the central axis J1 in the circumferential direction.

In the motor 1, when the plurality of blades 342 of the rotor fan 34 rotate in the circumferential direction, the flow of the air from the first opening 215 to the second opening 216 via the armature 22 and vicinity thereof is formed in the motor 1. In the motor 1, by rotating the rotor fan 34 in the direction opposite to the above, the flow of the air from the second opening 216 to the first opening 215 via the armature 22 and vicinity thereof may be formed in the motor 1. In either case, due to the air flow, the internal structure of the motor 1, in particular the armature 22, is cooled.

Hereinafter, the cooling by the rotor fan 34 will be described more specifically. In the motor 1, as the plurality of blades 342 of the rotor fan 34 rotate in the counterclockwise direction in the plan view, the air above the rotor fan 34 flows downward, and flows into the interior of the inner cylindrical portion 241 via the upper end opening in the inner cylindrical portion 241 of the bus bar holding portion 24. As a result, the air outside the housing 21 flows into the housing 21 via the plurality of first openings 215, and flows downward toward the rotor fan 34 rotating inside the inner cylindrical portion 241.

The inner cylindrical portion 241 rectifies the flow of air flowing into the rotor fan 34 and the flow of air sent out from the rotor fan 34 in a direction parallel to the central axis J1. Accordingly, the blowing efficiency by the rotor fan 34 can be improved. The air that passes through the inner cylindrical portion 241 and flows out downward from the lower end opening of the inner cylindrical portion 241 expands outward in the radial direction along the lower surface 246 of the flange portion 242 and the outer surface of the central protrusion portion 326 of the connection portion 323 and flows downward toward the armature 22. The air passes downward through the gap between the coil 224 of the armature 22 and the gap between the armature 22 and the rotor main body 32, flows downward, and flows out of the housing 21 via the plurality of second openings 216.

Accordingly, as described above, a flow of air from the first opening 215 to the second opening 216 via the armature 22 and the vicinity thereof is formed inside the motor 1. As a result, the internal structure of the motor 1, particularly the armature 22, is cooled. The first opening 215 is an inlet through which air flows into the interior of the motor 1 and the second opening 216 is an outlet through which air inside the motor 1 flows out.

On the other hand, in a case where the plurality of blades 342 of the rotor fan 34 rotate in the clockwise direction in the plan view, a flow of air from the second opening 216 to the first opening 215 via the armature 22 and the vicinity thereof is formed in the motor 1. As a result, the internal structure of the motor 1, particularly the armature 22, is cooled in the same manner as described above. In this case, the second opening 216 is an inlet through which air flows into the motor 1, and the first opening 215 is an outlet through which air inside the motor 1 flows out.

As described above, the rotor assembly 30 includes the shaft 31 made of a non-magnetic material and the cylindrical rotor main body 32. The shaft 31 has the central axis J1 along the up and down direction as a center. The rotor main body 32 is fixed to the outer surface of the shaft 31. The rotor main body 32 includes the plurality of core pieces 321, the plurality of rotor magnets 322, and the connection portion 323 which is made of resin. The plurality of core pieces 321 are arranged around the shaft 31 in the circumferential direction. The plurality of rotor magnets 322 are arranged alternately with the plurality of core pieces 321 around the shaft 31 in the circumferential direction. The connection portion 323 connects the shaft 31 to the plurality of core pieces 321 and the plurality of rotor magnets 322. The inner ends of the plurality of rotor magnets 322 in the radial direction are closer to the shaft 31 than the inner ends of the plurality of core pieces 321 in the radial direction.

In the rotor assembly 30, no magnetic force acts between the shaft 31 and each of the rotor magnets 322. Therefore, when manufacturing the rotor assembly 30, it is possible to prevent the relative position between the shaft 31 and the plurality of rotor magnets 322 from being shifted by the magnetic force without using a positioning jig or the like. As a result, the manufacture of the rotor assembly 30 can be facilitated.

In the rotor assembly 30, the outer surfaces 325 of the plurality of core pieces 321 and the outer surfaces 363 of the plurality of rotor magnets 322 are positioned at the same positions in the radial direction. Accordingly, the relative positions between the plurality of core pieces 321 and the plurality of rotor magnets 322 can be easily determined when manufacturing the rotor assembly 30. As a result, the manufacture of the rotor assembly 30 can be further facilitated.

As described above, the method for manufacturing the rotor assembly 30 includes a step of disposing the shaft 31, which is made of a non-magnetic material and has the central axis J1 along the up and down direction as a center, in a center of the cylindrical metal mold 91 (step S11); a step of arranging the plurality of core pieces 321 around the shaft 31 in the circumferential direction (step S12); a step of arranging the plurality of rotor magnets 322 alternately with the plurality of core pieces 321 around the shaft 31 in the circumferential direction (step S13); and a step of connecting the shaft 31 to the plurality of core pieces 321 and the plurality of rotor magnets 322 by filling a space between the shaft 31, the plurality of core pieces 321, and the plurality of rotor magnets 322 with resin (step S14).

In step S12 described above, the outer surfaces 325 of the plurality of core pieces 321 abut against the inner surface 92 of the metal mold 91. In addition, in step S13, the outer surfaces 363 of the plurality of rotor magnets 322 abut against the inner surface 92 of the metal mold 91. The inner ends of the plurality of rotor magnets 322 in the radial direction are closer to the shaft 31 than the inner ends of the plurality of core pieces 321 in the radial direction.

According to the manufacturing method, as described above, it is possible to prevent the relative position between the shaft 31 and the plurality of rotor magnets 322 from being shifted by the magnetic force without using a positioning jig or the like. As a result, the manufacture of the rotor assembly 30 can be facilitated. In steps S12 and S13, the plurality of rotor magnets 322 and the plurality of core pieces 321 arranged alternately in the circumferential direction are coupled by using the magnetic force of the rotor magnet 322, whereby the plurality of rotor magnets 322 and the plurality of core pieces 321 can be easily positioned. In addition, the outer surfaces 363 of the plurality of rotor magnets 322 and the outer surfaces of the plurality of core pieces 321 can easily abut against the inner surface 92 of the metal mold 91 by using the magnetic force of the rotor magnet 322. Accordingly, the relative positions between the plurality of core pieces 321 and the plurality of rotor magnets 322 can be easily determined. As a result, the manufacture of the rotor assembly 30 can be further facilitated.

In the rotor assembly 30 and the motor 1 described above, various modifications are possible.

For example, in each rotor magnet 322 of the rotor assembly 30, the first region 353 is omitted from the upper end surface 351, and the second region 354 as the engagement surface may extend outward in the radial direction from the inner end of the upper end surface 351 in the radial direction. In addition, the first region 356 may be omitted from the lower end surface 352 and the second region 357 as the engagement surface may extend outward in the radial direction from the inner end of the lower end surface 352 in the radial direction. In each of the rotor magnets 322 of the rotor assembly 30, the engagement surface described above is not necessarily required to be provided, and may be omitted.

In the rotor assembly 30, the core recessed portion 324 may be omitted from the inner surface of each core piece 321. In addition, in the rotor assembly 30, the connection plate portion 33 may also be omitted.

In the rotor assembly 30, the outer surfaces of the plurality of core pieces 321 and the outer surfaces 363 of the plurality of rotor magnets 322 are not necessarily required to be positioned at the same positions in the radial direction, and one outer surface may be positioned outward the other outer surface in the radial direction.

The position of the first opening 215 may be appropriately changed on the upper side of the armature 22. For example, the first opening 215 may be disposed in the canopy portion 213 of the housing 21 instead of the side wall portion 211 of the housing 21. The position of the second opening 216 may be appropriately changed on the lower side than the armature 22. For example, the second opening 216 may be disposed in the side wall portion 211 of the housing 21 instead of the bottom portion 212 of the housing 21.

In the rotor assembly 30, substantially the entire outer surface 363 of each rotor magnet 322 may be exposed from the connection portion 323. In other words, substantially the entire outer surface 363 may be included in the exposed region 372. For example, in a case where a chamfering process is performed on the side edge portion of the outer surface 363 in the circumferential direction, a notch or the like formed by the chamfering process is covered by a resin and the upper and lower connection portions 323 of the rotor magnet 322 may be connected by the resin.

The shape, structure and material of each configuration of the motor 1 may be variously changed. For example, as illustrated in FIG. 11, the rotor fan 34 may be a member connected to the rotor main body 32. In the example illustrated in FIG. 11, the central protrusion portion 326 of the connection portion 323 extends to the vicinity of the first bearing 41, and the plurality of blades 342 are connected to the outer surface of the central protrusion portion 326, whereby the rotor fan 34 are formed.

The motor 1 is not necessarily limited to a three-phase motor, and may be various types of motors. The motor 1 may be used for various devices other than the axial flow fan.

The motor according to the present disclosure can be used as a motor for various purposes. The motor is preferably used for an axial flow fan.

Features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises.

While preferred embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims. 

What is claimed is:
 1. A rotor assembly comprising: a shaft including a non-magnetic material and a central axis extending along an up and down direction as a center; and a cylindrical rotor main body fixed to an outer surface of the shaft; wherein the rotor main body includes: a plurality of core pieces arranged around the shaft in a circumferential direction; a plurality of rotor magnets alternately arranged with the plurality of core pieces around the shaft in the circumferential direction; and a connection portion that is made of resin and connects the shaft to the plurality of core pieces and the plurality of rotor magnets; and inner ends of the plurality of rotor magnets in a radial direction are closer to the shaft than inner ends of the plurality of core pieces in the radial direction.
 2. The rotor assembly according to claim 1, wherein outer surfaces of the plurality of core pieces and outer surfaces of the plurality of rotor magnets are at same positions in the radial direction.
 3. A motor comprising: the rotor assembly according to claim 1; a bearing mechanism that rotatably supports the shaft of the rotor assembly; an armature that faces the rotor main body of the rotor assembly in the radial direction; and a housing that accommodates the rotor assembly therein.
 4. A method for manufacturing a rotor assembly, comprising: a) a step of disposing a shaft, which is made of a non-magnetic material and has a central axis extending along an up and down direction as a center, in a center of a cylindrical metal mold; b) a step of arranging a plurality of core pieces around the shaft in a circumferential direction; c) a step of arranging a plurality of rotor magnets alternately with the plurality of core pieces around the shaft in the circumferential direction; and d) a step of connecting the shaft to the plurality of core pieces and the plurality of rotor magnets by filling with resin a space between the shaft, the plurality of core pieces, and the plurality of rotor magnets; wherein in step b), outer surfaces of the plurality of core pieces abut against an inner surface of the metal mold; in step c), outer surfaces of the plurality of rotor magnets abut against the inner surface of the metal mold; and inner ends of the plurality of rotor magnets in a radial direction are closer to the shaft than inner ends of the plurality of core pieces in the radial direction. 